Cryptology ePrint Archive: Report 2014/407

Abstract: We present a symmetric-key predicate-only functional encryption system, SP-FE, which supports functionality for regular languages described by deterministic finite automata. In SP-FE, a data owner can encrypt a string of symbols as encrypted symbols for matching. Later, the data owner can generate predicate tokens of the transitions in a deterministic finite automaton (DFA). The server with these tokens can decrypt a sequence of encrypted symbols correctly and transfer from one state to another accordingly. If the final state belongs to the set of accept states, the server takes assigned operations or returns the corresponding encrypted data. We have proven SP-FE preserves both plaintext privacy and predicate privacy through security analysis and security games. However, to achieve predicate privacy, we put bounds on the length of a string and the number of states of a DFA. Due to these restrictions, SP-FE can only capture finite languages. Finally, we present the performance analysis of SP-FE and mention possible future work.